Blankets for supporting solar cells have generally utilized substrates made of Kapton, which is a polyimide composition. It has been learned that Kapton is subject to attack by atomic oxygen which exists in low-earth orbits. Because Kapton does have many desirable characteristics, and has been so widely used for support blankets, efforts were made to protect the Kapton from atomic oxygen by coating it with substances which are resistant to it. Silicon dioxide has generally been used for this purpose. However, in use and over time, this coating tends to crack, and the Kapton is attacked by atomic oxygen which passes through the cracks.
It is an object of this invention to provide a support blanket which is inherently resistant to attack by atomic oxygen, and is not subject to degradation by it.
Support blankets for solar cell arrays which are to be used in space should be lightweight and flexible. Further, internal stresses which can be generated during thermal cycles should be minimized. Also, the blanket should be a good electrical insulator, and preferably also be a good thermal conductor.
Because the woven strands of the blanket and the solar cells are the stiffest parts of the assembly, they are the driving or determinant elements which tend to generate internal stresses. A close match of their coefficients of thermal expansion will result in less stress than would be generated by a combination of elements which have a greater difference in their coefficients. For example, Kapton's coefficient of thermal expansion is very much larger than that of a silicon solar cell, while the coefficients of the glass fibers used in this invention and a solar cell are closer by at least one magnitude. With this invention, these coefficients can be much more closely matched.
Furthermore, with this Invention a very compatible adhesive can be used between the blanket and the cells, which is advantageous both chemically and structurally.
Accordingly, it is another object of this invention to provide a blanket/solar cell system in which internal stresses are significantly reduced, compared to conventional systems.